1. Field of the Invention
The present invention relates to a free-piston type Stirling cycle engine.
2. Description of the Related Art
An example of a conventional Stirling cycle engine of this type is disclosed in Japanese Patent Unexamined Publication No. 2001-355513. The disclosed Stirling cycle engine has a piston and a displacer slidably inserted into a cylinder provided within a casing, the piston being reciprocated by a driving mechanism. When the piston is operated by the driving mechanism so that it travels in the cylinder and comes close to the displacer, a gas, which is in a compression chamber provided between the piston and the displacer, is compressed and flows into an expansion chamber provided between a distal end of the displacer and a distal portion of the casing, through a heat dissipating fin, a regenerator and a heat absorbing fin. Accordingly, the displacer is pushed downwardly with a predetermined phase difference relative to the piston. On the other hand, when the piston travels in the cylinder away from the displacer, the inside of the compression chamber is subjected to negative pressure, and the gas in the expansion chamber flows back to the compression chamber through the heat absorbing fin, the regenerator and the heat dissipating fin. Accordingly, the displacer is pressed upwardly with the predetermined phase difference relative to the piston. Throughout these processes, a reversible cycle consisting of two changes: an isothermal change; and an isochoric change is carried out, and thus a part adjacent to the expansion chamber is brought into a low-temperature state and a part adjacent to the compression chamber is brought into a high-temperature state. The Stirling cycle engine also has spiral blade springs to control the operation of the piston and the displacer. Center portions of respective blade springs are connected to the piston and the displacer, while edges of the respective blade springs are fixed to a flange-shaped mount provided on an outer peripheral surface of the cylinder by a connecting arm. This mount fixes the cylinder to the casing, while the cylinder supports the driving mechanism. Meanwhile, the above publication also discloses a method for forming the above-described cylinder having the mount. The method roughly shapes the cylinder by forging and casting, and then cuts it by machining, forming the connecting arm in a long screw shape so as to be screwed to the mount.
The above-described Stirling cycle engine, however, has following problems when the mount and the connecting arm are combined together by a connecting means because these components are separated pieces. That is, it requires production equipment such as mould for producing the mount and the connecting arm individually, as well as respective assembling processes for these components. Thus production costs are relatively high. Besides, the accuracy of the Stirling cycle engine as a whole depends on the accuracy of the respective components and the accuracy of individual assembling process. This makes it difficult to improve the accuracy of the Stirling cycle engine as a whole. For example, in a case where the aligning adjustment of the piston to the displacer is difficult, the Stirling engine may not be assembled at the worst. Further, according to the above-mentioned conventional art aiming at easily producing the cylinder and the mount at low costs, the improvement of the accuracy in the conventional Stirling cycle engine would become more difficult because the accuracy in assembling these cylinder and mount also is required.